Evolution of polyphenols content in plum fruits (Prunus salicina) with harvesting time by second-order excitation-emission fluorescence multivariate calibration

Abstract

Phenolic extracts from pulp and skin of Japanese plums Angeleno variety, sampled in May and September harvest, were analysed by excitation-emission fluorescence spectroscopy. The exploratory analysis of fluorescence second-order multivariate data was carried out by parallel factor analysis (PARAFAC) and catechin, epicatechin, procyanidin B2, chlorogenic acid and neochlorogenic acid were identified, by comparison of the corresponding PARAFAC loading profiles with their fluorescence spectra. In addition, a central composite design was employed for the determination of catechin, epicatechin, gallic acid, procyanidin B2, caffeic acid, neochlorogenic acid and chlorogenic acid concentrations in plum samples. In the validation set good recoveries were obtained for all analytes except for gallic and caffeic acids. The results obtained in the quantification of these compounds in plum samples were compared with the analysis by HPLC and the results showed that the levels of catechin plus epicatechin and of chlorogenic plus neochlorogenic acids decreased from May to September and these concentrations were higher in the skin than in the pulp. Furthermore, noticeable differences in the number of components were obtained depending on the maturation stage of plums, according to studies in both skin and pulp, separately.